The present invention relates to an image display apparatus such as a head-mounted display and a projector, which enlarges an original image displayed on an image display element and displays an enlarged image thereof.
A head-mounting type image display apparatus (head-mounted display: hereinafter, referred to as an “HMD”) has been used which enlarges an image (original image) displayed on an image display element such as a CRT and an LCD and displays the enlarged image thereof through an optical system.
Since this HMD is mounted on a head of an observer, reductions in size and weight thereof are required. On the other hand, it is desired that the HMD have a good optical performance and can provide an enlarged image as large as possible.
However, when the optical system is made small, distortion and axial chromatic aberration are generated, which makes it difficult to achieve a good optical performance. On the contrary, when the optical system is designed to reduce generation of the distortion and various aberrations, it is difficult to reduce the size of the optical system. Therefore, an HMD has been proposed which electrically corrects the distortion and the chromatic aberration of the optical system to reduce a load for aberration corrections of the optical system, thereby enabling miniaturization of the HMD.
For example, an HMD has been disclosed in Japanese Patent Laid-Open No. 6-265815 which improves an apparent resolution by synthesizing images displayed in two liquid crystal panels on a retina of an observer. This HMD electrically distorts (corrects) the images displayed on the liquid crystal panels such that an influence of the distortion generated by an optical system is canceled.
Moreover, an HMD has been disclosed in Japanese Patent Laid-Open No. 2001-186442 which outputs right and left video signals while temporally alternately switching them to one image display element, and causes image light to alternately enter into right and left eyes in synchronization with the switching of the right and left video signals. This HMD electrically distorts (corrects) the right and left video signals such that distortions generated by right and left optical systems are respectively canceled.
Performing such electric distorting correction on the image output to the image display element like the HMDs disclosed in the above-mentioned publications so as to cancel the distortion of the optical system can cause the observer to view an image with reduced distortion. The electric distorting correction is hereinafter referred to as the “inverse-correction”, and an image to which the inverse-correction was made is referred to as an inversely-corrected image.
However, when displaying the inversely-corrected image on the image display element with a high pixel number, moire fringe (interference fringe) generated by interference between regularly-arranged pixels and the distorted image may be observed. Therefore, even if the resolution of the image display apparatus is improved, the moire fringe will provide discomfort to the observer.